Wang Yuchuan, Tsui Benjamin M W
Division of Medical Imaging Physics, Department of Radiology, Johns Hopkins Medical Institutions, Baltimore, MD 21287, USA.
IEEE Trans Med Imaging. 2007 Mar;26(3):298-308. doi: 10.1109/TMI.2006.887372.
To further improve pinhole single photon emission computed tomography (SPECT) imaging, there have been increasing interests in the use of nonstandard collimator designs and/or acquisition geometries. Homogeneous coordinates provide a compact and convenient framework to unify the geometric descriptions of the projection operators for these different imaging geometries, which may facilitate the implementation of iterative reconstruction algorithms and the investigation of crucial geometric calibration problems in pinhole SPECT. In this work, these advantages were demonstrated through three examples, namely, multipinhole SPECT, pinhole SPECT with a helical scanning orbit, and pinhole SPECT with dual detectors. Specifically, we showed adaptable implementations of iterative image reconstruction algorithms and translatable strategies for efficient geometric calibrations through unifying projection operators of the aforementioned imaging geometries. Notably, the unified geometric descriptions of multipinhole and single pinhole projection operators allowed us to derive that one can effectively calibrate a multipinhole geometry using only two point sources without measuring their distance. Experimental studies were performed to demonstrate the validity of our approaches, which may be extended to other pinhole SPECT and cone-beam X-ray computed tomography imaging geometries.
为了进一步改进针孔单光子发射计算机断层扫描（SPECT）成像，人们对使用非标准准直器设计和/或采集几何结构的兴趣日益浓厚。齐次坐标提供了一个紧凑且方便的框架，用于统一这些不同成像几何结构的投影算子的几何描述，这可能有助于迭代重建算法的实现以及针孔SPECT中关键几何校准问题的研究。在这项工作中，通过三个例子展示了这些优势，即多针孔SPECT、具有螺旋扫描轨道的针孔SPECT以及具有双探测器的针孔SPECT。具体而言，我们通过统一上述成像几何结构的投影算子，展示了迭代图像重建算法的适应性实现以及用于高效几何校准的可转换策略。值得注意的是，多针孔和单针孔投影算子的统一几何描述使我们能够推导出，仅使用两个点源而无需测量它们的距离就可以有效地校准多针孔几何结构。进行了实验研究以证明我们方法的有效性，这些方法可能会扩展到其他针孔SPECT和锥束X射线计算机断层扫描成像几何结构。
